A third criticizes Brown’s reaction to the Sandy Hook Elementary School massacre that claimed 20 children and six teachers, after which Brown became the first GOP senator to back a federal ban of assault weapons: “You jumped on the bodies of children and said the gun was at fault.”

Brown met with the Gun Owners of New Hampshire on Tuesday and, according to a video of the event, staked out a centrist’s turf, clearly on defense as he contended with libertarian-minded activists openly distrustful of a former officeholder from Massachusetts.

The footage lays bare one component of Brown’s challenge as he attempts a political transition to a new state. Having lost his 2012 reelection bid to Elizabeth Warren, Brown and his wife have sold their home in Wrentham and moved full time to the family vacation home in Rye, N.H. He is now vying in a Republican primary for the chance to face US Senator Jeanne Shaheen, a popular Democrat seeking her second term.

Brown’s move has brought with it a new electorate, one far less progressive than the one in Massachusetts and openly leery of outsiders.

The 35-minute video, which was obtained by the Globe and ends abruptly when Brown requests the recorder stop taping, shows an often confrontational meeting, one that Brown aides said lasted nearly two hours at the Holiday Inn in Concord. According to published reports, dozens of demonstrators gathered outside the closed-door meeting, protesting what they viewed as Brown’s insufficient record of defending the Second Amendment.

‘I have no issue with regard to large-capacity magazines, at all. . . . I don’t care. It doesn’t matter to me. It’s not even in the conversation.’

In an e-mail, Brown’s campaign manager, Colin Reed, said, “Scott Brown supports the Second Amendment and he always appreciates the opportunity to meet with gun owners.”

Throughout the video, Brown, who retired earlier this month as a colonel in the National Guard, pushes back against activists eager for better management from the federal government and, in particular, Obama.

“He is the commander in chief. I will treat him with the due respect that it deserves,” Brown says.

Impeachment, Brown explains at one point, originates in the House, not the Senate.

“The best way to have a check and balance against the president of the United States right now is to have a Republican Senate,” he offers.

On the Second Amendment, he volunteers opposition to gun-free zones, a core issue for gun rights advocates. And he is seemingly supportive of the right to firearms that contain large amounts of ammunition.

“I have no issue with regard to large-capacity magazines, at all. . . . I don’t care. It doesn’t matter to me. It’s not even in the conversation. I’m not quite sure how else to say that,” he says.

In the video, Brown says Bloomberg is supporting Shaheen in the current race. Bloomberg has made no public endorsement in the race but has donated to the Senate Majority PAC, a Democrat-backing political action committee that has aired ads attacking Brown.

Brown at one point also notes that “I went to serve in Afghanistan.” In 2011, as part of his National Guard training, Brown went to a military base near Kandahar. In the afterword of his memoir, “Against All Odds,” Brown wrote, “I dressed in fatigues and battle armor, carried a side arm in my holster, and lived, worked, ate, and slept alongside fellow US soldiers and Guard members.”

Brown also encounters friction in a discussion of the United Nations. When he asserts that the international body has a role, at least two men in the audience push back, saying the UN does not have a role in New Hampshire.

When Brown encourages one member of the audience to call New Hampshire US Representative Ann Kuster with her complaints about management of the federal government, the woman insists her protests would go unheard.